Society of Systematic Biologists Has the Biological Species Concept Outlived Its Usefulness? Author(s): Paul R. Ehrlich Source: Systematic Zoology, Vol. 10, No. 4 (Dec., 1961), pp. 167-176 Published by: Taylor & Francis, Ltd. for the Society of Systematic Biologists Stable URL: http://www.jstor.org/stable/2411614 Accessed: 04-01-2016 19:22 UTC Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://www.jstor.org/page/ info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Taylor & Francis, Ltd., Society of Systematic Biologists and Oxford University Press are collaborating with JSTOR to digitize, preserve and extend access to Systematic Zoology. http://www.jstor.org This content downloaded from 132.248.28.28 on Mon, 04 Jan 2016 19:22:34 UTC All use subject to JSTOR Terms and Conditions SYMPOSIUM ON PHILOSOPHICAL SYSTEMATICS 167 more than abstract logical forms and catego- REFERENCES ries. They are habits, predispositions,deeply BRIDGMAN,P. W. 1936. The nature of physi- engrained attitudes of aversion and prefer- cal theory. Dover Publications, New York. ence. Moreover, the conviction persists- CLAUSEN, J. 1960. A simple method for the though history shows it to be a hallucination sampling of natural populations. Scottish -that all the questions that the human mind Plant Breeding Sta. Report: 69-73. has asked are questions that can be answered DARWIN, C. 1859. The origin of species. in terms of the alternatives that the questions DEWEY, C. 1957. The influenceof Darwinism themselves present. But in fact intellectual on philosophy. In M. GARDNER(ed.), Great progress usually occurs through sheer aban- essays in science. Pocket Library, Henry donment of questions together with both of Holt, New York. the alternatives they assume-an abandon- HARRINGTON,W. 1954. Flora of Colorado. ment that results from their decreasing vi- PERRY, J. W. 1960. Theory of documentation tality and a change of urgent interest. We do and strategy of searching. Apr. 12 and 13, 1960, Cleveland, Ohio. Contract No. AF 49 not solve them: we get over them. Old ques- (638)-357. (mimeographed). tions are solved by disappearing, evaporating, while new questions corresponding to the NORMAN H. RUSSELL, JR. is Professor of changed attitude of endeavor and preference Botany at Arizona State University, Tempe, take their place . ." (Dewey, reprint 1957) Arizona. Has the BiologicalSpecies Concept OutlivedIts Usefulness? PAUL R. EHRLICH IN THE PRESENT PAPER I would the "modern synthesis" in evolution liketo considerthe following question: would deny that reproductiveisolation is Is the biologicalspecies concept a use- a major factorin the evolutionaryprocess. ful taxonomictool? I do not wish to re- It does, however, seem pertinentto ques- examine the philosophicalquestion of tion (even at the risk of being accused whetheror not therereally are distinct of embracing the heresies of typologyand entitiesin nature which correspondto anti-evolutionism) using this isolation as our idea of "biological species." This a criterion for a taxonomic grouping. problemhas been dealt with fully by Grant (1957:74-75) states Burma (1954), Mayr (1957a), and others. "Accordingto the biologicalspecies concept In additionI will ignorethe relatedques- the species is a populationset apart fromthe tion of the degree to which apparent rest of the livingworld by reproductiveiso- structuringin natureis an artifactcaused lating mechanisms.Its boundariestherefore shouldbe markedby a prominentgap in the by the structuringof the vertebratecen- variationpattern. Good discretespecies are tral nervous systemor by the thought in factfound in all majorplant groups. These patternscharacteristic of Western culture. well-definedspecies, however, constitute only Whateverits degreeof reality,there is a fractionof the populationsin theirrespec- no doubt that in the past the biological tivephylads. The botanistfinds problematical species intermixedin varying proportions species concepthas been usefulin help- withgood species in mostof the familiesand ing to shape our thinkingabout evolu- genera. This is in markedcontrast with the tionaryproblems. No one familiarwith situationwhich the zoologistfinds in higher This content downloaded from 132.248.28.28 on Mon, 04 Jan 2016 19:22:34 UTC All use subject to JSTOR Terms and Conditions 168 SYSTEMATIC ZOOLOGY animals in which clearly circumscribedspe- words,forms having a wide spatial dis- cies are a rule and poorlydefined ones the ex- tribution,hut superficiallynot showing ception." greatgeographic variation, were not con- In a sample survey of some genera of sideredas presentingany problemat the plants, Grant found the percentage of species level-althoughinterfertility may "good" (i.e., distinct or easily delimited) not always existwhere it is assumed. species to range from 0 (California The genera of NorthAmerican butter- Ceanothus) to 100 (North American fliesare groupedbelow (somewhatarbi- Asclepias). trarily)into seven categories,according There seems to be general agreement to the frequencyof "good" species found that the biological species concept has withinthem. It was ratherdifficult, in no meaning whatever when one is deal- manycases, to decideexactly which cate- ing with asexual organisms, and is quite gorywas properfor a givengenus, which limited in its applicability in planfts. in itselfwould cast doubt on the overall However, what of the higher animals utilityof the speciesconcept. If biological where "circumscribedspecies are the rule species were readily recognizable,we and poorly defined ones are the excep- would have no difficultyin classifying tion?" Mayr (1957b) has suggested that generaaccording to the proportionof dis- analyses such as were done by Grant tinctspecies found within them. should be carried out for as many groups Group 1. Generain which the species of plants and animals as possible. As a seem quite distinct,and are considered preliminarystep in considering the use- by most workersto presentno serious fulness of the concept, I have done suc'h problems: Parnassius, Neophasia, Phoe- a survey of a group with which I am bis, Lethe, Euptoieta, Poladryas, Micro- familiar, the Nearctic butterflies (Papil- tia, Nymphalis, Vanessa, Anartia, Caly- ionoidea) . copis, Erora, Brephidium, Apodemia. , There are few, if any, groups of equiva- Group2. Generain whichmost species lent size that are as well-known systema- seemdistinct, but the status of some forms tically as the butterflies.Vast collections is in doubtat the presenttime: Eurema, of them have been amassed, and the litera- Anthocaris, Euchloe, Euptychia, Erebia, ture is replete with observations on their Ministrymon,Euristrymon, Strymon, Phi- distribution and (to a lesser degree) lotes. their genetics and behavior. If the bio- Group 3. Genera in which many or logical species concept is useable, it most forms present serious problems: should be easily applicable to a well- Papilio, Pieris, Oeneis, Speyeria, Boloria, known, diploid and outcrossing group of Euphydryas, Chlosyne, Phyciodes, Poly- "higher" animals such as the Nearctic gonia, Precis, Limenitis, Anaea, Libythea, butterflies. Chlorostrymon,Satyrium, "Thecla," Cal- In my survey of the butterflies,several lophrys,Lyeaena, Plebejus, Everes. things were done which would tend to Group4. Generain which,at the pres- overemphasize the utility of the biol6gi- ent stateof our knowledge,the biological cal species concept. First of all I was species conceptis virtuallyinapplicable: surveyinga limitedfauna, and it is widely Colias, Coenonympha, Cercyonis. admitted that species are more clearcut Group 5. Generawhich are monobasic: when viewed within a limited geographi- Paramecera, Neominois, Agraulis, DJryas, cal area. Thus the problem of the specific Dryadula, Habrodais, Hypaurotis, Phaeo- distinctness (or lack of same) of the strymon,Chrysophanus, Dolymorpha, Hy- Nearctic representatives of Holarctic postrymon, Panthiades, Glaucopsyche, formswas not considered. In addition the Phaedrotes, Cetastrina. question of possible undetected repro- Group 6. Genera which are not well ductive barriers was ignored. In other representedin the Nearcticregion, but This content downloaded from 132.248.28.28 on Mon, 04 Jan 2016 19:22:34 UTC All use subject to JSTOR Terms and Conditions SYMPOSIUM ON PHILOSOPHICAL SYSTEMATICS 169 best informationwould indicate that they tween the Palaearctic and Nearctic forms belong in Group 1 or Group 2: Nathalis, recentlylumped as vau-album. For many Anteos, Historis, Eumaeus, Leptotes. years the Nearctic form was considered Group 7: Genera which are not well specifically distinct and went under the represented in the Nearctic region, but name j-album. best informationwould indicate that they Erebia is a genus typical of those belong in Group 3 or Group 4: Battus, in which most species seem distifict Graphium, Parides, Enantia, Lycorella, (Group 2). Ignoring the status problem Heliconius, Metamorpha, Hypolimnas, of our members of Holarctic series, and Myscelia, Diaethria, Eunica, Mestra, the possible reproductive incompatibility Hamadryas, Biblis, Dynamine, Marpesia, of individuals from various populations Apatura, Tmolus, Cyanophrys, Atlides, of widely and